Heretofore, as a data storage processing device (network storage server) based on the client/server model to be commonly used by a plurality of users via network, there has been a network file system server which connects a juke box having a built-in magnetic disc and a magneto-optical disc to a workstation and loaded with device driver, unique file system and management software of the file device on a part of its operating system on the workstation.
This network file system server uses a software which makes the computer storage/file server connected to the network usable as if it were its own computer storage via the network. More specifically, it mounts the storage of the other computer in the directory on its computer via the network. By means of this network file system server the user can connect the network storage having large capacity to his own computer via the network and can utilize it.
The special features of this network file system server are: firstly, by making use of high speed of the magnetic disc file server, bit cost decreases by connecting the Juke box. Secondly, all removable storage media in the juke box are controlled as one volume. This means that the system controls the volume of removable media as an extended space of the magnetic disc and the user cannot use individual removable media freely.
Furthermore, thirdly, the network file system server has adopted the file system which treats the Juke box as a part of the magnetic disc and the server deals with only one file system. Fourthly, by conducting automatic file migration between storage hierarchy of the magnetic disc and the juke box, access speed approaches to the magnetic disc. Also by physically connecting a plurality of juke boxes, it is defined as an infinite large capacity file. Lastly, its management target is only on-line storage and does not exchange media during the system working condition, nor perform off-line media management.
Thus, the network file system server has the storage construction of which semiconductor memory, magnetic disc, optical disc and magneto-optical disc are hierarchized according to the access speed, and controls resources which the server has by means of hierarchical storage management.
However, since the hierarchization according to access speed is conducted in the NFS server, the device which brings the access turn around time closer to the access time of high speed storage such as the magnetic disc, has been derived. However, since the on-line storage capacity management for each client has not been conducted, it has created a problem that unfairness occurs among clients concerning the on-line capacity of storage which the client has. Here, the client indicates the client in the client/server model.
Furthermore, since the hierarchical management has been conducted only for the on-line storage, it has created a problem that the storage media cannot be exchanged during the system working condition when using storage having removable storage media which allows the magneto-optical disc to be removed. This means that the media containing users' files cannot be accessed at all after the system starts operating.
Moreover, there are various file systems corresponding to the quality of data and characteristics of storages at the present. However, since the hierarchical storages are treated as one large volume, it is a problem that only one file system can exist in the system. This means that users' files and data which are constructed by the file system unsupported by the system cannot be accessed.
Furthermore, there is a tendency that each client's file and data increase on the on-line storage. On the other hand, since files having low access frequency and files which are no longer accessed are held on the on-line storage, the usability of on-line storage decreases. Also, since the removable media are totally controlled by the system, it has created a problem that the client cannot handle explicitly the removable storage media which he has in the system.
The present invention has been done considering the above points and is proposing a data storage processing apparatus which is capable of improving the usability of the user as well as removing the unfairness among users.